Washing machine

ABSTRACT

Disclosed is a washing machine. In order to reduce excessive vibration, the washing machine is provided with suspensions between a casing and an outer tub, in which a suspension positioned at one side of the casing and a suspension facing the suspension positioned at one side of the casing are installed so that their damping forces can be asymmetric to each other. Accordingly, even if excessive vibration occurs at the time of an initial dehydration process, the outer tub inclined to a driving unit is prevented from colliding with the casing.

RELATED APPLICATION

The present invention relates to subject matter contained in priorityKorean Application No. 10-2007-0076580, filed on Jul. 30, 2007, which isherein expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine, and moreparticularly, to a washing machine capable of preventing an outer tubinclined toward a driving unit from colliding with an external casing atthe time of an initial vibration occurrence, and capable of effectivelyreducing excessive vibration by asymmetrically installing suspensions,in which the outer tub is supported by installing suspensions having arelatively large damping force at a side where a large load occurs dueto the driving unit, etc.

2. Description of the Background Art

Generally, a washing machine serves to wash laundry by using a softeningprocess by detergent, a frictional process by water stream occurring aswashing blades rotate, an impact process by washing blades, etc. Byusing a motor as a main driving force, the washing machine performs awashing process, a rinsing process, and a dehydrating process so as towash laundry with using detergent and water. The washing machinecomprises a motor serving as a driving unit, a mechanical part fortransmitting energy to laundry, a controller for controlling washingprocesses, a water supply unit for supplying water, and a water drainunit for discharging water.

The washing machine is largely divided into a cylinder type, an agitatortype, and a pulsator type according to washing methods.

According to the agitator type, an agitator protruding from the centerof an inner tub with a wing shape is rotated in right and leftdirections thus to wash laundry. According to the pulsator type, laundryis washed by using turbulent stream occurring as a disc-shaped pulsatoris rotated. According to the cylinder type, water, detergent, andlaundry are put into a drum having a plurality of protrusions, and thenare rotated with a low speed in a horizontal axis, thereby washinglaundry by an impact occurring as the laundry is lifted and dropped bythe protrusions.

FIG. 1 is a schematic sectional view of a washing machine in accordancewith the related art, FIG. 2 is a sectional view taken along line‘II-II’ of FIG. 1, and FIG. 3 is a sectional view of a suspension of thewashing machine of FIG. 1

Referring to FIGS. 1 and 2, a washing machine 10 comprises a body or acasing 1 that forms appearance; an outer tub 2 mounted in the casing 1;an inner tub 3 mounted in the outer tub 2; and a suspension apparatus orsuspensions 4 each having another end connected to a lower side of theouter tub 2, and configured to support the outer tub 2.

A driving unit 12 for driving the inner tub 3 is installed below theouter tub 2. The driving unit 12 is connected to a speed change portion14 installed at a lower central part of the outer tub 2 by a belt 16.

Here, the driving unit 12 is installed so as to be eccentric from thecenter (C) of the outer tub 2 by a predetermined distance (W).

Referring to FIG. 3, the suspension 4 comprises a damper cap 4 binstalled below the outer tub 2; a connection rod 4 a having one endpenetrating the damper cap 4 b, and another end mounted to the casing 1;a damper spring 4 c mounted in the damper cap 4 b, and configured toabsorb vibration from the outer tub 2; and a damper base 4 d installedat a lower opening of the damper cap 4 b, and configured to support theconnection rod 4 a or the damper spring 4 c.

A narrow air gap 5 is formed between the damper cap 4 b and the damperbase 4 d, and extension springs 6 are installed below the damper base 4d.

The extension springs 6 serve to extend a lower portion of the damperbase 4 d.

Each of the extension springs has both ends separated from each other,i.e., a non-consecutive circumference. Since non-consecutive part doesnot come in contact with the damper base 4 d, the extension springs 6 donot consecutively contact a lower portion of the damper base 4 d.

The suspensions 4 serve to reduce a very large vibration or amplitudeoccurring by a resonance at the time of excessive vibration (i.e., atthe time of starting a dehydration process).

According to a basic vibration reducing mechanism, vibration occurringfrom the inner tub 3 is reduced by a viscous damping force occurring asair is discharged through an air hole (not shown) of the damper cap 4 b,and by a frictional damping force occurring as the damper cap 4 b andthe damper base 4 d come into friction with each other. Here, excessivevibration or amplitude is reduced by a viscous damping force.

However, the conventional mechanism has the following problems.

An air gap 5 which allows a reciprocation of the washing machine isformed between the damper cap 4 b and the damper base 4 d. If thewashing machine 10 is used by approximately 1000 cycles, a clearance ofthe air gap 5 increases to allow a large amount of air to leak throughthe air gap 5. This causes a viscous damping force to be greatlylowered, thereby not reducing excessive vibration.

Furthermore, since the driving unit 12 is eccentrically installed fromthe center (C) below the outer tub 2, an initial static deflection ofthe outer tub 2 is toward the driving unit 12.

More concretely, as shown in FIG. 2, an interval (D2) between the casing1 disposed at a side of the driving unit 12 and the outer tub 2 isnarrower than an interval (D1) facing the D2. Accordingly, collisionbetween the casing 1 and the outer tub 2 may occur when the washingmachine is initially operated.

SUMMARY OF THE INVENTION

Therefore, it is a first object of the present invention to provide awashing machine capable of preventing an outer tub inclined towards adriving unit from colliding with a casing at the time of an initialvibration occurrence, by supporting the outer tub by installingsuspensions having a relatively large damping force at one side where alarge load occurs due to the driving unit, etc., and by installingsuspensions having a relatively small damping force at another sidefacing the one side.

It is a second object of the present invention to provide a washingmachine capable of preventing an outer tub from colliding with a casingby installing suspensions having a large damping force at a side of adriving unit by mounting a base cap to a lower opening of a damper cap,in which a small amount of air leakage occurs even if an air gap betweenthe damper cap and the damper base is widened.

It is a third object of the present invention to provide a washingmachine capable of absorbing excessive vibration occurring at a sidehaving a large initial deflection due to a load of a driving unit, byasymmetrically arranging suspensions to each other.

It is a fourth object of the present invention to provide a washingmachine capable of effectively reducing excessive vibration by mountingsuspensions having an extension spring to an opposite side to a side ofa driving unit, the extension spring consecutively contacting a damperbase in a circumferential direction.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a washing machine having a plurality of suspensionsinstalled between a casing and an outer tub, in which the suspensionshave different damping forces.

Here, the suspension installed at one side of the casing has a dampingforce different from that of the suspension installed at another sidefacing the one side. Preferably, the suspension installed at one side ofthe casing where an interval between the casing and the outer tub isrelatively narrower due to inclination of the outer tub has a dampingforce larger than that of the suspension installed at another sidefacing the one side.

Under the above configuration, the outer tub inclined toward the casingis prevented from colliding with the casing at the time of an initialdriving, thereby preventing noise occurrence and reducing excessivehorizontal vibration from the outer tub.

A driving unit for driving an inner tub installed in the outer tub ismounted to a lower surface of the outer tub, and the driving unit iseccentrically installed at a side toward which the outer tub isinclined.

When the driving unit is eccentrically installed from the center of theouter tub, the outer tub is inclined due to a weight or load of thedriving unit, thereby narrowing an interval between the casing and theouter tub. However, since suspensions having a damping force areinstalled at a side of the driving unit, collision between the casingand the outer tub can be prevented.

Each of the suspensions having a relatively large damping force(hereinafter, will be called as ‘first suspensions) among thesuspensions includes a damper cap mounted to the outer tub; a connectionrod having one end installed via the damper cap; a damper spring mountedin the damper cap; a damper base mounted to one end of the damper cap,and configured to support another end of the connection rod or one endof the damper spring; and a base cap mounted to a lower side of thedamper cap. As the base cap is mounted to the lower side of the dampercap, air leakage through an air gap between the damper cap and thedamper base is prevented thus to increase a viscous damping force.

Each of the suspensions having a relatively small damping force(hereinafter, will be called as ‘second suspensions) among thesuspensions includes a damper cap mounted to the outer tub installed inthe casing; a connection rod having one end installed via the dampercap; a damper spring mounted in the damper cap; a damper base mounted toone end of the damper cap, and configured to support another end of theconnection rod or one end of the damper spring; and a base cap mountedto a lower side of the damper cap. An air hole through which a viscousdamping force occurs is formed at the damper cap or the base cap.

Since air is leaked through the air hole formed at the damper cap or thebase cap, the second suspensions have a smaller viscous damping forcethan the first suspensions.

Instead of the second suspensions, one or more third suspensions may beused as suspensions having a relatively small damping force. The thirdsuspension include a damper cap mounted to the outer tub installed inthe casing; a connection rod having one end installed via the dampercap; a damper spring mounted in the damper cap; a damper base mounted toone end of the damper cap, and configured to support another end of theconnection rod or one end of the damper spring; and a base cap mountedto a lower side of the damper cap. An air hole through which a viscousdamping force occurs is formed at the damper cap or the base cap.

Here, the third suspensions have a smaller viscous damping force thanthe second suspensions due to no base cap provided thereat.

The second suspensions may be used as suspensions having a relativelylarge damping force, and one or more third suspensions may be used assuspensions having a relatively small damping force. That is, withconsideration of an initial deflection or a load of the washing machine,suspensions having different damping forces may be selected from thefirst to third suspensions.

According to another aspect of the present invention, there is provideda washing machine having a plurality of suspensions installed between acasing and an outer tub, in which so as to reduce excessive vibration ofthe washing machine, the suspensions installed at one side of the casingand the suspensions installed at another side facing the one side havedamping forces asymmetrical to each other.

Here, the suspensions having a relatively large damping force areinstalled at a side where a large load occurs due to a driving unit fordriving an inner tub inside the outer tub. Accordingly when the washingmachine is initially operated, collision between the casing and theouter tub is prevented.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic sectional view of a washing machine in accordancewith the related art;

FIG. 2 is a sectional view taken along line ‘II-II’ of FIG. 1;

FIG. 3 is a sectional view of a suspension of the washing machine ofFIG. 1;

FIG. 4 is a schematic sectional view of a washing machine according tothe present invention;

FIG. 5 is a sectional view of a suspension of the washing machine ofFIG. 4 according to a first embodiment of the present invention;

FIG. 6 is a perspective view of a damper base mounted to the suspensionof FIG. 5;

FIG. 7 is a sectional view of a suspension of FIG. 5 according to asecond embodiment of the present invention;

FIGS. 8A to 8C are views respectively showing an extension springmounted to the damper base of FIG. 6;

FIGS. 9A to 9C are modification examples of the extension spring of FIG.8; and

FIG. 10 is an experimental graph comparing excessive horizontal andvertical vibration of the present invention with that of the related artwhen suspensions of the present invention and the related art are used,respectively.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Hereinafter, configurations and operations of a washing machineaccording to a first embodiment of the present invention will beexplained in more detail with reference to the attached drawings.

Explanation for well-known configurations or functions will be omitted.And the same reference numerals will be given to the same parts as thoseof the aforementioned configurations, and their detailed explanationwill be omitted.

FIG. 4 is a schematic sectional view of a washing machine according tothe present invention.

As shown in FIG. 4, a washing machine 100 comprises a casing 110 thatforms appearance; an outer tub 120 mounted in the casing 110, andconfigured to store washing water therein; an inner tub 130 mounted inthe outer tub 120, and configured to receive laundry; and suspensions140 installed at four corners of the casing 110, and configured toelastically support the outer tub 120.

A driving unit 12 (refer to FIG. 1) for driving the inner tub 130 isinstalled below an outer surface of the outer tub 120. The driving unit120 is installed so as to be eccentric from the center of the outer tub120, and is connected to a speed change portion 14 (refer to FIG. 1)installed at a central part of the outer tub 120 by a belt 16 (refer toFIG. 1).

Here, the driving unit may be implemented as a direct drive motor. Themotor may include various motors such as an induction motor.

An interval (D4) between the casing 110 and the outer tub 120 at a side(‘A’ in FIG. 4) where the driving unit is installed is narrower than aninterval (D3) between the casing 110 and the outer tub 120 at a side(‘B’) facing the ‘A’. That is, the outer tub 120 is inclined toward theside of ‘A’ due to weight of the driving unit.

Here, suspensions having a damping force larger than that of suspensionsinstalled at the side of ‘B’ are mounted to the side of ‘A’ toward whichthe outer tub 120 is inclined. Accordingly, suspensions having arelatively small damping force are mounted to the side of ‘B’. That is,a damping force of the suspensions installed at the side of ‘A’ isdifferent from, or asymmetric to a damping force of the suspensionsinstalled at the side of ‘B’.

Under the configuration, collision between the outer tub 120 and thecasing 110 due to excessive horizontal vibration when the washingmachine 100 is initially operated can be prevented.

Hereinafter, in more detail, will be explained configurations of thesuspensions 140 installed at the side of ‘A’ where an interval betweenthe outer tub 120 and the casing 110 is relatively narrower, and thesuspensions 140′ installed at the side of ‘B’ facing the side of ‘A’.

FIG. 5 is a sectional view of a suspension of the washing machine ofFIG. 4 according to a first embodiment of the present invention, FIG. 6is a perspective view of a damper base mounted to the suspension of FIG.5, and FIG. 7 is a sectional view of a suspension of FIG. 5 according toa second embodiment of the present invention.

FIG. 5 shows the suspension 140 installed at the side of ‘A’ where aninterval between the outer tub 120 and the casing 110 is relativelynarrower. Referring to FIG. 5, the suspension 140 includes a damper cap142 mounted to the outer tub 120; a connection rod 141 having one endinstalled via the damper cap 142; a damper spring 143 mounted in thedamper cap 142; a damper base 145 mounted to one end of the damper cap142, and configured to support another end of the connection rod 141 orone end of the damper spring 143; and a base cap 146 mounted to a loweropening of the damper cap 142. For convenience, the suspensions 140 willbe referred to as ‘first suspensions’.

An upper portion of the damper cap 142 of the first suspensions 140 isupwardly extending like a neck of a bottle, and the upwardly extendingportion encompasses the connection rod 141.

The connection rod 141 is positioned inside the damper cap 142 via athrough hole 142 a formed at the upper portion of the damper cap 142.One end of the through hole 142 a is protruding to inside of the dampercap 142, thereby constituting a connection rod supporting portion 142 cthat encompasses and supports the connection rod 141.

One end of the connection rod 141 is fixed to a connection rod fixingportion 145 c of the damper base 145. Preferably, the connection rodfixing portion 145 c is protruding from an upper side of the damper base145, and has a predetermined height so as to stably support theconnection rod 141.

A plurality of protrusions 145 d are formed on an outer circumferentialsurface of the connection rod fixing portion 145 c. The plurality ofprotrusions 145 d are forcibly inserted into an inner circumferentialsurface of the damper spring 143, thereby stably supporting the damperspring 143.

A lower end of the damper spring 143 is supported by the protrusions 145d on the surface of the connection rod fixing portion 145 c, and anupper end of the damper spring 143 is supported by a spring supportingportion 142 b formed on an inner surface of the damper cap 142.

At an initial state, i.e., at a state that the washing machine is notprovided is with washing water or laundry therein, the damper spring 143preferably maintains a compressed state, and the damper base 145 forsupporting the damper spring 143 is positioned at an inner side of alower end of the damper cap 142. The reason is as follows. Once laundryor washing water is introduced into the inner tub 130, the damper spring143 is extended due to a weight of the laundry or washing water, and thedamper base 145 moves to a lower side of the damper cap 142. Here, ifthe damper base 145 is positioned at the end of the damper cap 142,laundry, etc. is introduced into the inner tub 130, and the damper base145 is completely separated from the damper cap 142.

Here, the damper spring 143 is preferably a compression coil spring, butis not limited thereto. As the damper spring 143, any elastic meanshaving an elastic restoration force and configured to absorb orattenuate vibration can be used. For example, a rubber member may beused to connect one end of the connection rod 141 and the connection rodfixing portion 145 c of the damper base 146. Also, a rubber pillar (notshown) having a cavity therein may be used as the damper s spring 143.

When the damper spring 143 is used as an elastic means, one end of theconnection rod 141 positioned in the damper cap 142 is preferablydisposed in the damper spring 143.

Between an inner surface of the damper cap 142 and an outermostcircumference of the damper base 145, a minute air gap 150 is formed. Africtional damping process occurs through the air gap 150.

The base cap 146 is mounted to a lower opening of the damper cap 142,and is coupled to the damper cap 142 by a hook (not shown) formed at thedamper cap 142 with receiving the damper base 145 therein. In order toensure a sealed state inside the damper cap 142, the damper cap 142 andthe base cap 146 may be coupled to each other by forming a screw threadat a coupling portion therebetween.

Extension springs 148, 149 may be mounted to a lower side of the damperbase 145. The damper base 145 will be explained in more detail withreference to FIG. 6. The connection rod fixing portion 145 c connectedto one end of the connection rod 141 is formed above the damper base145, and the plurality of protrusions 145 d are provided on an outercircumferential surface of the connection rod fixing portion 145 c. Aspring supporting portion 145 e is integrally formed below theconnection rod fixing portion 145 c. Preferably, the spring supportingportion 145 e has a wide area so as to sufficiently support the damperspring 143.

A skirt portion 145 f having an area wider than that of the springsupporting portion 145 e is integrally formed below the springsupporting portion 145 e.

Here, the skirt portion 145 f is in a thin cylindrical shape having apredetermined height, and an air gap 150 is formed between an outersurface of the skirt portion 145 f and an inner surface of the dampercap 142.

A plurality of slits 145 b are formed at the skirt portion 145 f in aheight direction, and extension springs 148 and 149 are mounted to aninner surface of the skirt portion 145 f. Here, in order to prevent theextension springs 148 and 149 from being separated from the skirtportion 145 f, a concaved groove (not shown) or a stopping jaw 145 a isformed on an inner surface of the skirt portion 145 f.

Since the extension springs 148 and 149 are mounted to the skirt portion145 f with a diameter decreased than the original diameter, they have anelastic restoration force to restore the original diameter. Due to theelastic restoration force, the edge of the damper base 145 is extendedto an inner surface of the damper cap 142. That is, the skirt portion145 f is pushed to the damper cap 142 thus to be extended. Here, theskirt portion 145 f can have a large extension degree by having theplurality of slits 145 b. The skirt portion 145 f can be outwardlyextended even by the extension springs 148 and 149 having a smallelastic restoration force.

Either the stopping jaw 145 a or the slits 145 b, or both the stoppingjaw 145 a and the slits 145 b can be formed with consideration of thesize of the damper base 145, or an elastic force of the extensionsprings 148 and 149, etc.

Since a lower opening of the damper cap 142 of the first suspension 140is blocked by the base cap 146, a viscous damping force by air insidethe damper cap 142 is very large. When the inner tub 130 is in aseverely excessive vibration state, air inside the damper cap 142 is notdischarged out thus to damage the damper cap 142. In order to preventthe damage of the damper cap 142, an air hole (not shown) is preferablyformed at the damper cap 142.

Accordingly, the most preferably, the first suspensions 140 areinstalled at the side of ‘A’.

Hereinafter, the suspensions 140′ having a smaller damping force thanthe first suspensions 140 will be explained in more detail withreference to FIG. 7. For convenience, the suspensions 140′ of FIG. 7will be referred to as ‘second suspensions’. The second suspension 140′has the same configuration as the first suspension 140, except that anair hole 147 is formed at a base cap 146′ so as to implement a smallerdamping force than the first suspension 140. That is, while air insidethe damper cap 142 is discharged out through the air hole 147 of thebase cap 146′, a viscous damping force occurs. Accordingly, the secondsuspensions have a smaller damping force than the first suspensions 140.

If an air hole (not shown) is formed at the damper cap 142 of the firstsuspension 140, an additional air hole (not shown) has to be formed atthe damper cap 142 of the second suspension 140′ so as to implement adamping force of the second suspension 140 to be smaller than that ofthe first suspension 140.

More concretely, the second suspension 140′ has the same configurationas the first suspension 140, except that an air hole 147 is furtherformed at a base cap 146′. The air hole 147 may be formed at the dampercap 142 or the base cap 146′ of the second suspension 140′. The air hole147 of the damper cap 142 may be blocked by a lubricant such as greasedeposited onto the surface of the damper cap 142, whereas the air hole147 of the base cap 146′ has a low possibility to be blocked by alubricant. One or more suspensions having a smaller damping force thanthe second suspensions 140′ may be mounted to an opposite side to thefirst suspensions 140, which will be referred to as ‘third suspensions’.

The third suspensions have the same configuration as the firstsuspensions 140 or the second suspensions 140′ from which the base caps146 and 146′ are removed, respectively. That is, the third suspensionhas the damper cap 142 with a lower side thereof opened. However, thedamper base 145 is mounted to the third suspension.

The third suspension may occur air leakage through an air gap 150between the damper cap 142 and the damper base 145. Therefore, it isimportant to manage abrasion of the air gap 150. To this end, theextension springs 148 and 149 have to make an important role.Hereinafter, the extension springs 148 and 149 of the third suspensionwill be explained in more detail. The configuration of the extensionsprings of the first suspensions 140 and the second suspensions 140′ areequal to that of the third suspensions.

FIGS. 8A to 8C are views respectively showing an extension springmounted to the damper base of FIG. 6, and FIGS. 9A to 9C aremodification examples of the extension spring of FIG. 8.

As shown in FIG. 8, the extension spring 148 of the third suspension isin a ring shape having a consecutive circumference. That is, when viewedfrom the front, the extension spring 148 is in an approximate ring shape(refer to FIG. 8B), whereas when viewed from the side, the extensionspring 148 has some parts overlapping each other in a longitudinaldirection (refer to FIG. 8C). That is, the extension spring 148 is woundso that both ends thereof can overlap each other by a predeterminedlength.

Here, curved portions 148 a and 148 b are formed at both ends of theextension spring 148 toward the center of the extension spring 148. Thecurved portions 148 a and 148 b are used to mount the extension spring148 to the damper base 145. When the curved portions 148 a and 148 b arepressed at both sides, a diameter of one side of the extension spring148 is decreased to allow the extension spring 148 to be easily mountedto the damper base 145. Then, when the curved portions 148 a and 148 bare released, the extension spring 148 is restored to the originalstate. At the same time, the skirt portion 145 f is outwardly extended.

As shown in FIG. 8A, the extension spring 148 consecutively contactslower side surfaces of the damper base 145, i.e., the skirt portion 145f due to its consecutive circumference, and contacts all parts of theskirt portion 145 f. Accordingly, the air gap 150 between the damper cap142 and the damper base 145 is uniformly maintained in a circumferentialdirection of the extension spring 148, thereby preventing non-uniformclearance of the air gap 150.

As the extension spring 148 having a consecutive circumference is used,the skirt portion 145 f of the damper base 145 is prevented from beingflatly abraded even when coming into friction with an inner surface ofthe damper cap 142.

FIGS. 9A to 9C are modification examples of the extension spring of FIG.8.

Referring to FIG. 9, the extension spring 149 has the same shape as theextension spring 148 of FIG. 8, except that there are no curved portionsat both ends thereof.

When viewed from the front, the extension spring 149 is in a ring shapehaving a consecutive circumference (refer to FIG. 9B), whereas whenviewed from the side, the extension spring 149 has some partsoverlapping each other in a longitudinal direction (refer to FIG. 9C).The extension spring 149 can maintain its elastic restoration force fora long time due to its overlapping parts, and can be easily mounted tothe skirt portion 145 f. That is, once the extension spring 149 is heldby a user with its central part being pressed, a diameter of one side ofthe extension spring 149 is decreased to allow the extension spring 149to be easily mounted to the skirt portion 145 f.

The extension spring 148 of FIG. 8 has the same shape as the extensionspring 149 of FIG. 9, except that the curved portions 148 a and 148 bare formed at both ends thereof. Accordingly, the extension springs 148and 149 can be fabricated by using the same molding pattern. Moreconcretely, the extension spring 148 of FIG. 8 can be fabricated by amolding pattern of the extension spring 149 of FIG. 9, and then byforming two curved portions at both ends thereof in a pressing manner,etc. Accordingly, one molding pattern can be used to fabricate two typesof extension springs, which enhances the productivity.

The third suspension can constantly maintain the air gap 150 between thedamper cap 142 and the damper base 145 by using the extension springs148 and 149, thereby increasing a viscous damping force by air leakedthrough the air gap 150.

The third suspension is implemented so that the damper cap 142 has alower opening to which the base caps 145 and 145′ have not been mounted,thereby occurring air leakage more than the first suspensions 140 or thesecond suspensions 140′. Accordingly, the third suspensions have adamping force smaller than that of the first suspensions 140 or thesecond suspensions 140′.

When suspensions having different damping forces are to be installed,suitable suspensions are selected from the first to third suspensionsthus to be arranged so that damping forces can be asymmetric to eachother centering around the center of the outer tub 120.

That is, when the first suspensions are used to have a large dampingforce, either the second suspensions 140′ or the third suspensions areselected as suspensions having a small damping force. On the contrary,when the second suspensions 140′ are used to have a large damping force,the third suspensions are selected as suspensions having a small dampingforce. For these selections, a load of a driving unit or a mechanicalpart, or an initial deflection of the outer tub have to be considered.

FIG. 10 is an experimental graph comparing excessive horizontal andvertical vibration or amplitude of the present invention where the firstsuspensions 140 are mounted to the side of ‘A’ and the secondsuspensions 140′ are mounted to the side of ‘B’, with that of therelated art where suspensions symmetrical to each other are used.Referring to FIG. 10, the horizontal axis shows horizontal and verticalvibration of the outer tub 120, whereas the vertical axis shows anamplitude (mm) according to the vibration. Referring to FIG. 10,according to the present invention where the first suspensions 140 aremounted to the side of ‘A’ toward which the outer tub 120 is inclinedand the second suspensions 140′ are mounted to the side of ‘B’ facingthe ‘A’, a horizontal amplitude was increased by 1.01 mm than theconventional one, but a vertical amplitude was decreased by 5.27 mm from19.84 mm to 14.57 mm. That is, when the suspensions 140 and 140′ of thepresent invention are used, excessive vibration is decreased byapproximately 27% to the maximum than the conventional one.

So far, the present applicant explained about the washing machine, butthe present invention may be applied not only to the washing machine,but also to various fields such as a washing machine compatible with adrier, a dryer, or a combined washing system.

Also, in the present invention, it was explained that the outer tub isinclined to one side due to eccentric installation of a motor such asthe driving unit. However, when a direct drive motor is used, or when aload of the driving unit or the mechanical part is not completelysymmetrical to each other in a circumferential direction centeringaround the center of the outer tub, the outer tub may be inclined to oneside. The latter case may be applied to claims of the present invention.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteachings can be readily applied to other types of apparatuses. Thisdescription is intended to be illustrative, and not to limit the scopeof the claims. Many alternatives, modifications, and variations will beapparent to those skilled in the art. The features, structures, methods,and other characteristics of the exemplary embodiments described hereinmay be combined in various ways to obtain additional and/or alternativeexemplary embodiments.

As the present features may be embodied in several forms withoutdeparting from the characteristics thereof, it should also be understoodthat the above-described embodiments are not limited by any of thedetails of the foregoing description, unless otherwise specified, butrather should be construed broadly within its scope as defined in theappended claims, and therefore all changes and modifications that fallwithin the metes and bounds of the claims, or equivalents of such metesand bounds are therefore intended to be embraced by the appended claims.

1. A washing machine having a plurality of suspensions installed betweena casing and an outer tub, wherein the suspensions have differentdamping forces.
 2. The washing machine of claim 1, wherein thesuspension installed at one side of the casing has a damping forcedifferent from that of the suspension installed at another side facingthe one side.
 3. The washing machine of claim 2, wherein the suspensioninstalled at one side of the casing where an interval between the casingand the outer tub is relatively narrower due to inclination of the outertub has a damping force larger than that of the suspension installed atanother side facing the one side.
 4. The washing machine of claim 3,wherein a driving unit for driving an inner tub installed in the outertub is eccentrically mounted to a lower surface of the outer tub, andthe outer tub is inclined due to the driving unit.
 5. The washingmachine of claim 1, wherein each of the suspensions having a relativelylarge damping force among the suspensions comprises: a damper capmounted to the outer tub; a connection rod having one end installed viathe damper cap; a damper spring mounted in the damper cap; a damper basemounted to one end of the damper cap, and configured to support theconnection rod or the damper spring; and a base cap mounted to a lowerside of the damper cap.
 6. The washing machine of claim 5, wherein eachof the suspensions having a relatively small damping force among thesuspensions comprises: a damper cap mounted to the outer tub installedin the casing; a connection rod having one end installed via the dampercap; a damper spring mounted in the damper cap; a damper base mounted toone end of the damper cap, and configured to support the connection rodor the damper spring; and a base cap mounted to a lower side of thedamper cap, wherein an air hole is formed at the damper cap or the basecap.
 7. The washing machine of claim 5, wherein each of the suspensionshaving a relatively small damping force among the suspensions comprises:a damper cap mounted to the outer tub installed in the casing; aconnection rod having one end installed via the damper cap; a damperspring mounted in the damper cap; a damper base mounted to one end ofthe damper cap, and configured to support the connection rod or thedamper spring; and an extension spring installed below the damper base,and configured to outwardly extend an edge of the damper base, whereinthe interval between the damper cap and the damper base is constantlymaintained in a circumferential direction by the extension spring. 8.The washing machine of claim 1, wherein each of the suspensions having arelatively large damping force among the suspensions comprises: a dampercap mounted to the outer tub installed in the casing; a connection rodhaving one end installed via the damper cap; a damper spring mounted inthe damper cap; a damper base mounted to one end of the damper cap, andconfigured to support the connection rod or the damper spring; and abase cap mounted to a lower side of the damper cap, wherein an air holeis formed at the damper cap or the base cap.
 9. The washing machine ofclaim 8, wherein each of the suspensions having a relatively smalldamping force among the suspensions comprises: a damper cap mounted tothe outer tub installed in the casing; a connection rod having one endinstalled via the damper cap; a damper spring mounted in the damper cap;a damper base mounted to one end of the damper cap, and configured tosupport the connection rod or the damper spring; and an extension springinstalled below the damper base, and configured to outwardly extend anedge of the damper base, wherein an interval between the damper cap andthe damper base is constantly maintained in a circumferential directionby the extension spring.
 10. A washing machine having a plurality ofsuspensions installed between a casing and an outer tub, wherein thesuspensions comprise first suspensions installed at one side of thecasing and second suspensions installed at another side of the casingfacing the first suspensions, and the first suspensions and the secondsuspensions have damping forces asymmetrical to each other.
 11. Thewashing machine of claim 10, wherein the first suspensions have adamping force larger than that of the second suspensions, and areinstalled at one side of the casing where a large load occurs due to aload of a driving unit provided to drive an inner tub, therebypreventing collision between the casing and the outer tub at the time ofan initial operation of the washing machine.
 12. The washing machine ofclaim 11, wherein each of the first suspensions comprises: a damper capmounted to the outer tub; a connection rod having one end installed viathe damper cap; a damper spring mounted in the damper cap; a damper basemounted to one end of the damper cap, and configured to support theconnection rod or the damper spring; and a base cap mounted to a lowerside of the damper cap.
 13. The washing machine of claim 12, whereineach of the second suspensions comprises: a damper cap mounted to theouter tub installed in the casing; a connection rod having one endinstalled via the damper cap; a damper spring mounted in the damper cap;a damper base mounted to one end of the damper cap, and configured tosupport the connection rod or the damper spring; and a base cap mountedto a lower side of the damper cap, wherein an air hole is formed at thedamper cap or the base cap.
 14. The washing machine of claim 12, whereineach of the second suspensions comprises: a damper cap mounted to theouter tub installed in the casing; a connection rod having one endinstalled via the damper cap; a damper spring mounted in the damper cap;a damper base mounted to one end of the damper cap, and configured tosupport the connection rod or the damper spring; and an extension springinstalled below the damper base, and configured to outwardly extend anedge of the damper base, wherein an interval between the damper cap andthe damper base is constantly maintained in a circumferential directionby the extension spring.